I have run across them that looked pretty from the outside then I got out the water hose and it looked like a mud slide on the slab.

I was going to add for mo-flo to check if the coil is a double row job. But then I read about the evap having a cap tube so that made me wonder if the condenser is just as ancient (thereby unlikely to have double coils).

Last summer I split apart many of the condenser coils at my building. The amount of dirt between the two coil sets was astounding. Just washing the coil from the front or back without splitting it wasn't doing anything for all the crap in the middle.

04-09-2005, 11:43 PM

tinknocker service tech

Quote:

Originally posted by mrbillpro

Quote:

Originally posted by tinknocker service tech some of the old cap tube coils ran low back arround 55 to 60.

This is true! Tin, we are telling our age. :D

i was told 32 years ago get out while you can stil do something else heheheh man i should have listened

04-10-2005, 12:16 AM

hvac-tech-lane

Condenser motor change. Check the HP rating, speed, and rotation also the fan position in the orfice is very important.
High head pressure is caused by not rejecting enough (quantity) of heat.
LL 115d, 78d Ambient, 37d approach too much.
Kinks would cause low pressures both sides.
High head pressures:
Dirty condenser
Overcharge (look for high subcooling)
Non condensibles
Low condenser airflow
Condenser air recirculation
High evap air flow and/or humidity causes elevated head
but not high head normally
Other causes also but rare.

04-10-2005, 12:41 AM

Milk man

I'm with everyone else, clean the condenser first. Even if it looks clean.

Can you open the plenum's door and watch the coil. I've ran into some that were not feeding every circuit. Someone overcharged them to get suction pressure up.

Also, is the CU newer. Maybe the old coil will not work with a higher seer unit.

04-10-2005, 03:11 PM

beenthere

Quote:

Originally posted by lynn rodenmayer

Also, is the CU newer. Maybe the old coil will not work with a higher seer unit.

Or is the CU a larger tonage then the cap tube indoor.

04-10-2005, 03:44 PM

mo-flo

the cu is about 15 years old....gonna give him a call and see if he wants me to clean it,but this will be added charge cause that don't come with a furn' changeout...i cleaned the indoor coil for him though,....also he said that the motor was bigger i'm assuming more hp....thanx for replies guys.

04-10-2005, 03:47 PM

mo-flo

also it is in modular home and the system is mismatched with evaporator made by someone else,...i would have to get file out....will take advice about watching tubes thanx.

04-10-2005, 04:27 PM

hvac-tech-lane

Quote:

Originally posted by beenthere

Quote:

Originally posted by lynn rodenmayer

Also, is the CU newer. Maybe the old coil will not work with a higher seer unit.

Or is the CU a larger tonage then the cap tube indoor.

beenthere, et.al
In the intrest of understanding the refregeration cycle better please explain how a oversized CU would cause high head pressure.

04-10-2005, 04:32 PM

Mr Bill

[QUOTE]Originally posted by hvac-tech-lane

Quote:

In the intrest of understanding the refregeration cycle better please explain how a oversized CU would cause high head pressure.

I would say probably because of smaller metering device with smaller evap. that will raise the head a tad higher than a normal matched system. Especially on the older cap tube stuff.

04-10-2005, 05:48 PM

hvac-tech-lane

[QUOTE]Originally posted by mrbillpro

Quote:

Originally posted by hvac-tech-lane

Quote:

In the intrest of understanding the refregeration cycle better please explain how a oversized CU would cause high head pressure.

I would say probably because of smaller metering device with smaller evap. that will raise the head a tad higher than a normal matched system. Especially on the older cap tube stuff.

How would a smaller metering device raise head pressure?

04-10-2005, 09:33 PM

Jax

I would check the sub cool to see how much liquid is stacking up. If the coil is clean, and fan is working properly that is about all the that can cause hi head. I would guess an under sized orifice or restriction in the liquid line would be the problem.
That alone does not raise head, but when someone just charges until they get the low up and fill the condenser with liquid, it sure will.
Jax

04-10-2005, 09:34 PM

beenthere

The only way it wouldn't is if it was a txv, sized for the outdoor unit.

An over sized CU, would have a very low suction pressure at normal head pressures because the cap tube wouldn't have enough flow through it.

Some one may have miss matched it, and just kept adding gas till they got a decent suction pressure. Which means it has to have a high head pressure to force enough refrigerant through the cap tube to keep from freezing the coil.

04-10-2005, 11:36 PM

fireair

Replace Consenser Motor, Check for Horsepower and RPM. Make sure it is right rotator (CW/CCW) and suggestion to raise condenser coil with water hose.